I notice a huge amount of guest on webmaster, usually about 4000-5000.
Though, there are only about 100 registered users online at all times. I think if you limit the amount of threads guest is able to view then there will be more registered users online and more post/contribution.

regards,
Viral

More likely there would just be less people visiting the forum. Most people never register for a forum. They typically just read what's there, which is fine. I don't think we want to prevent people from viewing any of the public threads here. Those that want to join will and those that don't won't.